Combustion control with combustion air and draft diversion air control system



June 4, 1963 0. w POWERS 3,092,320

COMBUSTION CONTROL WITH COMBUSTION AIR AND DRAFT DIVERSION AIR CONTROL SYSTEM Filed Feb. 29, 1960 F lg 3 1 Fl 9. l

i l6 [L L i I, I 1 '-7 I I I f 1 x i L I 1' E UUUUE a f I20 5 l2 I40 l4 Transducer 43 Combustion Chamber Thermostat 3| INVENTOR Dwight W. Powers ill United States Patent 3,092,320 COMBUSTION CONTROL WITH COMBUSTION AIR AND DRAFT DIVERSION AIR CONTROL SYSTEM Dwight W. Powers, 8208 Perry Highway, Pittsburgh, Pa. Filed Feb. 29, 1960, Ser. No. 11,590 9 Claims. (Cl. 236-9) This invention relates to a combustion control with combustion air and draft diversion air control system for automatically fired heat exchanger units, and particularly to a safety damper control therein, that eliminates many of the dangers and undesirable operational features found in previous automatically fired heat exchanger units or systems.

Contemporary domestic heat exchanger units, furnaces, boilers, space heaters, water heaters, and the like, control their flow of fuel, with safety devices to stop such flow in the event of certain mis-operations. They provide for mixing the given fuel with primary air and secondary air for combustion in the combustion chamber. They provide a flue opening for the attachment of a fine, conduit, or stack, to vent the products of combustion to the chimney and thence to their dispersal in the outside atmosphere. They provide an in-built draft diverter or anticipate the use of a hood-type draft diverter in the stack, to relieve undue heat-draft through the combustion chamber and to prevent chimney downdrafts from reaching said combustion chamber. Their proper combustion, however, presumes the availability of sufficient air for combustion and their provision for venting the products of combustion further presumes the availability of sufficient air to replenish that which was used and exhausted, while also indicating some doubt of replenishment by arranging to prevent chimney down-drafts from reaching the combustion chamber.

The well known volume of air required for proper combustion of automatic feed fuels is at least 10 cubic feet of air per 1,000 B.t.u. fuel in-put. The addition of heat-draft diversion air causes an actual exhaustion of approximately cubic feet of air for each 1,000 B.t.u. fuel in-p ut. Thus, the operation of a furnace for one hour, with an A.G.A. rating of 180,000 B.t.u. per hour in-put, would exhaust 2,700 cubic feet of air up the chimney in that hour.

Contemporary automatically fired heat exchanger units provide for the intake of combustion air and draft diversion air from their immediate surroundings, through various grilles or openings in the unit's jacket or fan or draft diverter hood, and at least some installation instructions specify an opening in the outside wall of the room containing the heat exchange unit of a size equal to the size of the flue or stack leading into the chimney. Such wall openings however, even if created by builders or installers, are not maintained. Occupants subsequently plug up such openings, to stop the chilling of the area by the entering outdoor air.

Thus, it is apparent that contemporary automatically fired heat exchange units draw their considerable requirement of combustion air and draft diversion air from the internal living area air of the house or structure in which they are contained, and the replenishment of such used and exhausted air must occur through leakage, commonly known as crackage, from outside into perhaps every room of the house or structure being heated, via said crackage, around doors and windows, or in gusts with the opening of an outside door. One of the noticeable forms of this leakage is the lines of din, dust and soot left on window sills, and floors or wherever crackage occurs and cold drafts along floors. The warming of this cold outdoor air to liveable temperature requires more fuel consumption, which in turn demands more air for combustion and draft diversion to be exhausted up the chimney, the replenishment of which draws in still more cold outdoor air through crackage. This added heating requirement can alone account for one-fourth or more of the total fuel consumed.

In addition, if a house or structure is sufficiently sealed up to substantially eliminate crackage," a partial vacuum or air-pressure dropw may be created by the heat exchanger units operation, possibly contributing to a down-draft in the chimney or at least to the spilling of combustion fumes from the draft diverter into the living area air. Such failure of air replenishment also might contribute to incomplete combustion which is the chief source of dangerous carbon-monoxide. Unless sufficient replacement air is available for that air used by combustion and draft diversion and exhausted up the chimney, a nominally vented heat exchange unit,could be nearly as dangerous as though it were unvented altogether.

My new combustion control with combustion air and draft division air control system eliminates these problems and dangers by drawing all such air directly from the free outside air through an air inlet conduit leading to the combustion chamber and draft diverter of a heat exchange unit. The combustion chamber and draft diverter are enclosed and restricted against air access except from this outside source through the air inlet conduit. Said air inlet conduit accommodates the structure of my damper control and thus, accomplishes complete control of air supply, combustion chamber functioning, draft diverter functioning, and the venting of combustion products via vent-stack into the chimney; wholly separating those functions from any contact with living area air. The use of outdoor temperature air for combustion and draft diversion makes little or no change in a combustion chambers B.t.u. out-put from a given B.t.u. in-put, due to the high temperature at which combustion occurs. Also heat loss during non-combustion periods is minimized, as will be shown hereinafter.

Another advantage that my new combustion control with combustion air and draft diversion air control system provides, as compared with contemporary heat exchange units, is the accomplishment of maximum heat retention-or minimizing heat draft heat loss-in the combustion chamber, stack, and chimney, after the combustion cycle has terminated, without any need for damper devices on the exhaust side of the combustion chamber, which can be potentially dangerous in the event of misoperation. As is commonly known in the art, fuel will continue to burn in the combustion chamber for at least a short period of time after the room thermostat has reacted, and perhaps for longer periods of time in the event the fuel supply means fails to shut off. Failure of such dampers in the vent-stack, particularly failure to remain open long enough for the combustion of residue fuel, or to remain open in the even of continued combustion due to fuel valve failure, would contaminate living area air with the products of such unvented combustion, possibly causing annoying odors, smoke damage and danger to health and life.

Earlier attempts have been made to diminish heatdraft heat loss during non-combustion periods by damper closing the vent-stack. For example, see United States Patent No. 2,856,992 to Bartels and No. 2,633,299 to Brown. But neither Bartels nor Brown nor any other contemporary damper device known to the applicant pro vides safely for a situation where the fuel continues to burn for more than a minute or two. In this latter situation, all the aforesaid devices close the damper regardless, with the dangerous results above described ensuing.

My new combustion control with combustion air and draft diversion air control system eliminates these dangers by a more positive control over the retention of the 3 dampers open position, whereby the damper may not close until combustion in the combustion chamber is definitely at an end. Also my preferred location for said damper is on the air intake side of the heating unit in the conduit provided therefor so that the vcntstack is left unimpeded for the escape of smoke or fumes, yet accomplishing the diminishment of heat loss during non-coin bustion periods by the total stoppageor near-total stoppage where pilot lights must continue to burn-of airflow through the combustion chamber, stack and chimney.

I provide a combustion control with combustion air and draft diversion air control system for an automatically fired heat exchanger unit, furnace, boiler, space heater, water heater and the like, comprising an enclosure, which might be accomplished by modification of any existing jacket or housing design, to restrict all air access to the combustion chamber and draft diversion means to an outdoor air source, with my safety damper mounted in an air conduit duct leading from said outside source to the heating unit, the shutter plate of which may be rotated to open or close said conduit, fuel supply control means adapted to respond to damper position whereby fuel supply means may be activated only when said shutter plate is in open position, a double-wound solenoid having a moveable armature which responds to a transducer means, such as a room temperature thermostat or a water temperature thermostat or a steam pressure sensing device, and a combustion chamber thermostat, said damper shutter plate being rcsponsively connected to said armature whereby said shutter plate opens in response to movement of said armature upon activation of said solenoid, and biased spring means responsivcly connected to said armature whereby said damper plate swings to a closed position upon de-activation of both windings of said solenoid.

Other details, objects and advantages of the invention will become apparent as a present preferred embodiment thereof proceeds.

In the accompanying drawings, I have shown a present preferred embodiment of the invention in which FIGURE l is a schematic drawing of a heat exchange system in accordance with my invention;

FIGURE 2 is a schematic showing in isometric of a damper control system in accordance with my invention; and,

FIGURE 3 is a diagrammatic showing of a proposed circuit in accordance with my invention.

Referring to the drawings and initially to FIGURE 1, I have illustrated a combustion control with combustion air and draft diversion air control system in a domestic heating system wherein a heat exchanger unit has a combustion chamber 11, burners 12, and an air intake conduit 14 leading from a free air supply source outside the external surface of building into combustion chamber 11 and draft diversion duct 13 leading to ventstack 16. Thus, all combustion air for the combustion chamber 11 for combustion of fuel therein, and all draft diversion air to the vent-stack 16 for reduction of undue heat-draft through the combustion chamber 11, is drawn from a source removed from the interior air of the house or structure being heated. The combustion products exhaust conduit, or vent-stack 16 leads from combustion chamber 11 to a flue or chimney 17 and this vent-stack otTers no opening to or from the interior air of the house or structure being heated. Thus, the entire travel of combustion air and draft diversion air, from its outdoor source, to chimney 17, is completely enclosed and separated from the interior air of the house or structure containing unit 10, thereby preventing any use of, or contamination of, said interior air. Screen 22 is placed over the air intake opening in building 15 to keep leaves and the like from clogging up conduit 14.

Damper mechanism 18 may be located at access opening 14a of the heat exchange unit, or at some point within the length of air intake conduit 14, to permit or stop the flow of air to combustion chamber 11 and draft diverter duct 13. The stoppage of air-flow creates a static air condition in combustion chamber 11, draft diverter 13, ventstack 16 and chimney 17, and thereby retains the built-up heat from the just-completed combustion cycle therein throughout the non-combustion cycle. Thus, heat saving benefits result and too, it takes less time to attain proper draft condition with the commencement of the next combustion cycle. Further, damaging condensation, upon resumption of combustion, to the vent-stack and chimney otherwise cooled by the unrestricted passage of air therethrough is minimized.

Referring now to FIGURE 2, damper mechanism 18 comprises a shutter plate 19 mounted on an axis rod 20 the ends of which extend beyond the side edges of shutter plate 19 and are pivotally mounted at or in the side walls 23 of conduit 14 as shown in the present preferred embodiment, or at or in the side walls of heat exchange unit 10 adjacent opening 140. Shutter plate 19 may thus rotate degrees to an open or closed position with respect to conduit 14 or opening 14a. When in the closed position, shutter plate 19 substantially engages the top and bottom walls 24 as well as side walls 23 of conduit 14, to substantially close off the flow of air through conduit 14 to heating unit 10. Holes 34 in the face of the shutter plate 19 are provided only with pilot light type burner heat exchanger units and are of a size and number to permit only enough air-flow to heating unit 10 to maintain pilot light combustion when shutter plate 19 is closed. Shutter plate 19 is rotated by solenoid 25 having an armature 26 pivotally connected to crank 27 which is connected to axis rod 20 preferably externally of conduit 14. A spring 28 tied to anchor 29 is attached to armature 26 to bias shutter plate 19 to a closed position. Thus, when solenoid 25 is activated by the transducer 30, armature 26 is drawn to the right as shown in FIGURE 2, which causes crank 27 to rotate axis rod 20 and shutter plate 19 in the direction indicated by the arrow in FIGURE 2 to the open position, and when solenoid 25 is de-activated, spring 28 causes armature 26 to move to the left which in turn causes crank 27 to rotate axis rod 20 and shutter plate 19 in the reverse direction to closed position.

Referring now to FIGURE 3, solenoid 25 is preferably a double wound solenoid having windings 25a and 25b with single armature 26. Thus, solenoid 25 may be activated by either or both of the windings. ln applicants present preferred embodiment, winding 25a is connected in an electrical circuit including transducer 30. Transducer 30 for the instant illustration is a room air thermostat that is strategically located and set for the air temperature desired in building 15. In other applications of my invention it is clear that transducer 30 would take any of a different number of well known forms. For instance, in a hot water heater, transducer 30 would be a water temperature thermostat, and for a further instance, in a boiler transducer 30 may be any one of a number of Well known pressure sensing switch devices; or if it is a solid being heated, transducer 30 may be a thermocouple switch device. It is abundantly clear that the strict form of transducer 30 will depend upon the particular body being heated and since for the purposes of a present illustration I have placed my invention in the environment of a domestic heating unit, I have more particularly described transducer 30 as a room air temperature thermostat; however, applicant wishes it to be distinctly understood that he does not intend to limit himself thereto, but rather only to the scope of the claims. Thus, in the present illustrated application of my invention, when room thermostat 30 senses a need of heat, contacts within said thermostat 30 will close and conduct current from the power line 35, through line 37, through contacts within thermostat 30, through line 38, to winding 25:! of solenoid 25 and thence through line 39 to the power line 36; thus energizing solenoid 25 which causes armature 26 to move to the right, as pictured in FIGURE 2, and thereby open damper 18. As shown in the drawings (FIGURE 2) a mercury switch 32 is fixed to the axis rod 20, externally of conduit 14 but is alternatively mountable on the face of shutter plate 19, so that it rotates with shutter plate 19, from an open circuit position when shutter plate 19 is in closed position, to a closed circuit position when shutter plate 19 is in open position. Thus, when damper 18 is opened by the signal from thermostat 30, switch 32 is rotated to a closed circuit position completing a circuit from thermostat 30 through line 40, mercury switch 32, line 41, fuel supply mechanism 33 and line 42 to the power line 36; fuel supply mechanism 33 is thereby energized to furnish the necessary fuel through fuel supply line 12a to burners 12, required to produce the heat called for by room thermostat 30. Fuel supply mechanism 33 may be any one of a number of such mechanisms well known in the art to direct the supply of fuel to heat exchange unit 10, the type of mechanism being determined generally by the fuel employed.

With the commence of combustion in the heating cycle, the temperature adjacent to such combustion activates a thermostat 31, so mounted as to place its thermal sensing component adjacent to the combustion in the combustion chamber 11, causing its contacts to close. This completes a circuit from power line 35 through line 43, the contacts within switch 31, line 44, to winding 25b of solenoid 25, thence through line 45 to power line 36; which energizes winding 25b of solenoid 25 to thus apply a second damper opening force to that already applied by the aforementioned winding 25a of solenoid 25.

When the preselected room temperature is reached, the contacts within room thermostat 30 open to deenergize winding 25a of solenoid 25 and also de-energize fuel supply mechanism 33 causing it to cut off the flow of fuel to burners 12. After combustion is at an end in combustion chamber 11, the temperature in combustion chamber 11 will drop and cause the contacts in thermostat 31 to open and thus de-energize winding 25b of solenoid 25. Consequently, solenoid 25 is completely deactivated and this permits spring 28 to move armature 26 to the left, as pictured in FIGURE 2, to thereby close damper 18.

It is apparent that if for some reason or other the fuel supply to burners 12 is not cut off, or if there is a residue of fuel that causes combustion in combustion chamber 11 to continue for a time, thermostat 31 does not break its contacts and winding 25b continues to energize solenoid 25 to hold damper 18 open for so long as combustion continues in combustion chamber 11, thereby eliminating the dangers pointed out earlier.

Applicant wishes to point out the other solenoid arrangements may be made to accomplish the same result, such as two separate solenoids with common or separate armatures attached to crank 27, and means other than spring 28 to return shutter plate 19 to closed position; however, applicant prefers the present described structure because of its relative simplicity.

Summarizing, it is manifestly clear that so long as damper 18 is closed fuel supply mechanism 33 is deenergized by switch 32 and that so long as the fuel supply mechanism 33 is activated and fuel is being burned, damper 18 is held open; thus, double protection is afforded against the dangerous situation of having combustion take place with damper 18 closed.

While I have shown and described a present preferred embodiment of the invention, it is to be distinctly understood that the invention is not limited thereto but may be otherwise variously embodied within the scope of the following claims.

I claim:

1. An automatically fired heating unit comprising a combustion chamber including burner means therein, combustion air inlet means including conduit means to said combustion chamber, combustion products exhaust conduit means, transducer means responsive to a condition affected by the heating unit, thermostat means responsive to combustion chamber temperature, a damper member pivotally mounted within said inlet means and swingable to open and substantially close said inlet means, solenoid means having movable armature means linked to and driveable to swing said damper member, fuel supply conduit means for supplying fuel to said burner means, fuel supply control means responsive to said transducer means through a switch closed by movement of said damper member to open position whereby fuel is supplied to said burner means only when both the transducer means is calling for heat and the damper member is in open position, said solenoid means being energized by either of said transducer means and said combustion chamber thermostat means whereby said armature means moves to open said damper member when either the transducer means is calling for heat or the combustion chamber thermostat means senses combustion taking place in the combustion chamber, and bias means operative to close said damper member upon deenergizing of said solenoid means whereby said damper member is closed only when both the transducer means ceases to call for heat and the combustion chamber thermostat means senses combustion has ceased therein.

2. An automatically fired heating unit as claimed in claim 1 wherein the conduit means of said combustion air inlet means leads air to said combustion chamber from an air source outside the structure being heated.

3. An automatically fired heating unit as claimed in claim 1 wherein the switch closed by movement of said damper member to open position is a mercury switch mounted on said damper member so that when said damper is in open position, the mercury in said switch covers the contacts and closes the circuit said switch is disposed in and when said damper is in closed position said mercury is thereby removed from said contacts to open said circuit.

4. An automatically fired heating unit as claimed in claim 1 wherein said bias means is a spring connected to said armature means.

5. An automatically fired heating unit as claimed in claim 1 wherein said transducer means is a thermostat responsive to the temperature of a body being heated.

6. An automatically fired heating unit as claimed in claim 1 wherein said transducer means is a switch responsive to pressure sensing means.

7. An automatically fired heating unit comprising a combustion chamber including burner means therein, combustion air inlet means including conduit means to said combustion chamber, combustion products exhaust conduit means, draft diversion air conduit means leading from said inlet means to said exhaust conduit means, transducer means responsive to a condition affected by the heating unit, thermostat means responsive to combustion chamber temperature, a damper member pivotally mounted within said inlet means and swingable to open and substantially close said inlet means, solenoid means having moveable armature means linked to and driveable to swing said damper member, fuel supply conduit means for supplying fuel to said burner means, fuel supply control means responsive to said transducer means through a switch closed by movement of said damper member to open position whereby fuel is supplied to said burner means only when both the transducer means is calling for heat and the damper member is in open position, said solenoid means being energized by either of said transducer means and said combustion chamber thermostat means whereby said armature means moves to open said damper member when either the transducer means is calling for heat or the combustion chamber thermostat means senses combustion taking place in the combustion chamber, and bias means operative to close said damper member upon dcenergizing of said solenoid means whereby said damper member is closed only when both the transducer means ceases to call for heat and the combustion chamber thermostat means senses combustion has ceased therein.

8. An automatically fired heating unit as claimed in claim 7 wherein the conduit means of said combustion air inlet means leads air to said combustion chamber and draft diversion air conduit from an air source outside the structure being heated, said heating unit having sulficient air-tight integrity whereby substantially all combustion and draft diversion air is drawn from said outside source.

9. An automatically fired heating unit comprising a combustion chamber including burner means therein, combustion air inlet means including conduit means to said combustion chamber, combustion products exhaust conduit means, draft diversion air conduit means leading from said inlet means to said exhaust conduit means, said combustion air inlet conduit means leading air to said combustion chamber and draft diversion air conduit from an air source outside the structure being heated, said heating unit having sufiicient air-tight integrity whereby substantially all combustion and draft diversion air is drawn from said outside source, transducer means responsive to a condition affected by the heating unit, thermostat means responsive to combustion chamber temperature, a damper member pivotally mounted Within said inlet means and swingable to open and substantially close said inlet means, solenoid means having moveable armature means linked to and driveable to swing said damper member, fuel supply conduit means for supplying fuel to said burner means, fuel supply control means responsive to said transducer means through a mercury switch closed by movement of said damper member to open position whereby fuel is supplied to said burner means only when both the transducer means is calling for heat and the damper member is in open position, said solenoid means being energized by either of said transducer means and said combustion chamber thermostat means whereby said armature means moves to open said damper member when either the transducer means is calling for heat or the combustion chamber thermostat means senses combustion taking place in the combustion chamber, and spring bias means operative to close said damper member upon deenergizing of said solenoid means whereby said damper member is closed only when both the transducer means ceases to call for heat and the combustion chamber thermostat means senses combustion has ceased therein.

References Cited in the file of this patent UNITED STATES PATENTS 1,773,585 Klockau Aug. 19, 1930 2,184,983 Tornquist Dec. 26, 1939 2,490,855 Burns Dec. 13, 1949 2,619,022 Hergenrother Nov. 25, 1952 2,768,675 Conn Oct. 30, 1956 2,788,943 Fauser Apr. 16, 1957 FOREIGN PATENTS 527,568 Germany June 19, 1931 

1. AN AUTOMATICALLY FIRED HEATING UNIT COMPRISING A COMBUSTION CHAMBER INCLUDING BURNER MEANS THEREIN, COMBUSTION AIR INLET MEANS INCLUDING CONDUIT MEANS TO SAID COMBUSTION CHAMBER, COMBUSTION PRODUCTS EXHAUST CONDUIT MEANS, TRANSDUCER MEANS RESPONSIVE TO A CONDITION AFFECTED BY THE HEATING UNIT, THERMOSTAT MEANS RESPONSIVE TO COMBUSTION CHAMBER TEMPERATURE, A DAMPER MEMBER PIVOTALLY MOUNTED WITHIN SAID INLET MEANS AND SWINGABLE TO OPEN AND SUBSTANTIALLY CLOSE SAID INLET MEANS SOLENOID MEANS HAVING MOVABLE ARMATURE MEANS LINKED TO AND DRIVEABLE TO SWING SAID DAMPER MEMBER, FUEL SUPPLY CONDUIT MEANS FOR SUPPLYING FUEL TO SAID BURNER MEANS, FUEL SUPPLY CONTROL MEANS RESPONSIVE TO SAID TRANSDUCER MEANS THROUGH A SWITCH CLOSED BY MOVEMENT OF SAID DAMPER MEMBER TO OPEN POSITION WHEREBY FUEL IS SUPPLIED TO SAID BURNER MEANS ONLY WHEN BOTH THE TRANSDUCER MEANS IS CALLING FOR HEAT AND THE DAMPER MEMBER IS IN OPEN POSITION, SAID SOLENOID MEANS BEING ENERGIZED BY EITHER OF SAID TRANSDUCER MEANS AND SAID COMBUSTION CHAMBER THERMOSTAT MEANS WHEREBY SAID ARMATURE MEANS MOVES TO OPEN SAID DAMPER MEMBER WHEN EITHER THE TRANSDUCER MEANS IS CALLING FOR HEAT OR THE COMBUSTION CHAMBER THERMOSTAT MEANS SENSES COMBUSTION TAKING PLACE IN THE COMBUSTION CHAMBER, AND BIAS MEANS OPERATIVE TO CLOSE SAID DAMPER MEMBER UPON DEENERGIZING OF SAID SOLENOID MEANS WHEREBY SAID DAMPER MEMBER IS CLOSED ONLY WHEN BOTH THE TRANSDUCER MEANS CEASES TO CALL FOR HEAT AND THE COMBUSTION CHAMBER THERMOSTAT MEANS SENSES COMBUSTION HAS CEASED THEREIN. 